2-(2-oxo-5-(1,1,3,3-tetramethylbutyl)-2,3-dihydro-1-benzofuran-3-yl)-4-(1,1,3,3-tetramethylbutyl)phenyl acetate

Endpoint summary

Additional information

Toxicokinetic assessment

There were no studies available in which the toxicokinetic properties of the test substance were investigated. The test substance (molecular weight 350.5 g/mol) is a white powder (Chilworth, 2008) with a Log Pow of 9.6 (Bayer, 1999), a water solubility of < 100 µg/L at 20°C (Bayer, 1999), and a vapor pressure of 0.000000000807 Pa at 20°C (calculated, Bayer, 1999).

Absorption

Absorption via the gastrointestinal tract:

In an acute oral toxicity study, rats were administered single doses of the test article at 2000 mg/kg body weight. No mortality, necropsy findings and no signs of systemic toxicity were observed (Notox, 1999). In a repeated dose toxicity study (oral, 28 days), rats were administered up to 1000 mg/kg body weight per day of the test substance by gavage (Notox, 1999). Again, no mortalities, clinical signs, necropsy findings and so signs of systemic toxicity related to treatment were observed. Minor changes of statistical significance, when compared to controls, were recorded in some parameters of hematology, clinical biochemistry and body weight, however these changes were minimal and no dose response was present, therefore these changes were considered incidental and of no toxicological relevance. Consequently, the NOAEL in this study was determined to be 1000 mg/kg. In a one-generation reproduction toxicity study, the test substance was administered at dose levels of up to 1000 mg/kg to groups of male and female rats. Males were exposed for 99 or 100 days, i.e. 10 weeks prior to mating, during mating, and up to termination. Females were exposed for 57 to 63 days, i.e. during 2 weeks prior to mating, during mating, during post-coitum, and during at least 20 days of lactation. F0-females were allowed to produce and rear a litter until Day 21 of lactation. When compared to control animals no changes for mortality, clinical signs, body weight, food consumption, macroscopic examination, organ weights, microscopic examination, reproduction, breeding data and pup development were observed that were considered to be an effect of treatment. From the results presented in this report a definitive parental, reproduction, breeding and developmental NOAEL of at least 1000 mg/kg bw per day was established. Thus, the available oral toxicity studies do not indicate systemic availability of the test substance.

Absorption through the gastrointestinal tract is favored for molecules with a molecular weight below 500 g/mol; molecular weights above 1000 g/mol are not easily absorbed (ECHA GD 7c, 2008). Based on molecular weight the test substance could be absorbed in the gastrointestinal tract. The substance is characterized by low water solubility and is therefore not readily dissolved in gastrointestinal fluids. In addition, the log Pow of 9.6 does not favor absorption by passive diffusion. However, highly lipophilic compounds (log Pow > 4) that are poorly soluble in water may be taken up by micellular solubilisation (ECHA GD 7c, 2008), therefore absorption of the test substance cannot be completely ruled out. The available data from toxicity studies with oral administration, however, do not indicate systemic availability. Therefore, the substance is expected to be poorly absorbed through the gastrointestinal tract after oral ingestion.

Dermal absorption:

In an acute dermal toxicity study the LD50 was higher than 2000 mg/kg body weight and no signs of acute dermal toxicity were observed (Notox, 1999). In a guinea pig maximization test, the test article did not cause sensitization after dermal challenge application (Notox, 1999). These results do not indicate systemic availability of the test substance after dermal exposure. Highly lipophilic substances (log Pow > 4) that come into contact with the skin can readily penetrate the lipid rich stratum corneum but are not well absorbed systemically. The substance must be sufficiently soluble in water to partition from the stratum corneum into the epidermis. Therefore, if the water solubility is below 1 mg/l, dermal uptake is likely to be low (ECHA GD 7c, 2008). In conclusion, based on the low water solubility and log Pow of 9.6 together with the results of acute dermal and sensitization studies, dermal absorption of the test article is expected to be low.

Absorption via inhalation:

No information from acute or repeated dose toxicity studies is available, which could provide information about the systemic distribution of the test substance after inhalation. The test substance itself has an extremely low vapor pressure of 0.000000000807 Pa at 20°C (calculated, Bayer, 1999).Therefore, also considering its low water solubility, absorption of the substance vapor via the inhalative route is expected to be low.

Metabolism

Potential metabolites were calculated by OECD toolbox 2.2. Here, the simulator tools for liver proposed the elimination of acetic acid from the side chain by ester hydrolysis. Acetic acid is part of the endogenous metabolism and may be further metabolized within the citric acid cycle. Studies on genotoxicity (Ames-Test, chromosome aberration assay in CHO cells, micronucleus assay in-vivo) gave no indications of a reactivity of test substance or its metabolites under the test conditions (i.e. no increased mutagenicity or cytotoxicity in treatments with metabolic activation).

Excretion

In view of the absence of relevant findings and the expected low bioavailability, it can be assumed that the test substance is rapidly excreted. Since the test substance has a molecular weight larger than 300 g/mol and a low solubility in water, it is expected to be excreted predominantly via the feces (ECHA GD 7c, 2008).